Publications by authors named "Shingo Nakane"

8 Publications

  • Page 1 of 1

Clinical factors affecting evoked magnetic fields in patients with Parkinson's disease.

PLoS One 2020 17;15(9):e0232808. Epub 2020 Sep 17.

Department of Neurology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.

Studies on evoked responses in Parkinson's disease (PD) may be useful for elucidating the etiology and quantitative evaluation of PD. However, in previous studies, the association between evoked responses and detailed motor symptoms or cognitive functions has not been clear. This study investigated the characteristics of the visual (VEF), auditory (AEF), and somatosensory (SEF) evoked magnetic fields in patients with Parkinson's disease (PD), and the correlations between evoked fields and the patient's clinical characteristics, motor symptoms, and cognitive functions. Twenty patients with PD and 10 healthy controls (HCs) were recruited as participants. We recorded VEF, AEF, and SEF, collected clinical characteristics, performed physical examinations, and administered 10 cognitive tests. We investigated differences in the latencies of the evoked fields between patients with PD and HCs. We also evaluated the correlation of the latencies with motor symptoms and cognitive functioning. There were significant differences between the two groups in 6 of the cognitive tests, all of which suggested mild cognitive impairment in patients with PD. The latencies of the VEF N75m, P100m, N145m, AEF P50m, P100m, and SEF P60m components were greater in the patients with PD than in the HCs. The latencies mainly correlated with medication and motor symptoms, less so with cognitive tests, with some elements of the correlations remaining significant after Bonferroni correction. In conclusion, the latencies of the VEF, AEF, and SEF were greater in PD patients than in HCs and were mainly correlated with medication and motor symptoms rather than cognitive functioning. Findings from this study suggest that evoked fields may reflect basal ganglia functioning and are candidates for assessing motor symptoms or the therapeutic effects of medication in patients with PD.
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October 2020

The presence of short and sharp MEG spikes implies focal cortical dysplasia.

Epilepsy Res 2015 Aug 12;114:141-6. Epub 2015 May 12.

Department of Pediatrics, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-ku, Sapporo, Japan. Electronic address:

Purpose: This study focused on the characteristic needle-like epileptic spikes of short duration and steep shape seen on magnetoencephalography (MEG) in patients diagnosed with focal cortical dysplasia (FCD) morphologically. We aimed to validate the analysis of MEG spike morphology as a noninvasive method of identifying the presence and location of FCD.

Methods: MEG was collected by 204-channel helmet-shaped gradiometers. We analyzed MEG spike sources for 282 patients with symptomatic localization-related epilepsy. MEG showed clustered equivalent current dipoles when superimposed on their three-dimensional-magnetic resonance images (MRI) in 85 patients. Fifty-seven patients were excluded from our study, because they had destructive brain lesions or an insufficient number of spikes for statistical analysis. Twenty-eight patients (18 males, 10 females; aged 1-34 years) were finally matched to our inclusion criteria, and were categorized into three groups: FCD (7 patients), non-FCD (10 patients), and non-lesion (11 patients), based on the MRI findings. We measured the duration, amplitude, and tilt manually for at least 15 spikes per patient, and compared the three groups using a one-way analysis of variance, followed by the Tukey test when statistically significant (p < 0.05). In 17 patients with visible MRI lesions, we investigated the correlation between the depth of the lesion and the tilt using the Pearson product moment correlation.

Results: The average spike duration was significantly shorter in the FCD and non-lesion groups than in the non-FCD group (p < 0.05). The average amplitude was not significantly different between the three groups. The average spike tilt was significantly steeper in the FCD group than in the non-FCD group (p = 0.0058). There was no significant difference between FCD and non-lesion patients in both duration and tilt. Our additional study revealed a significant negative correlation between the depth of the lesion and the average tilt (p = 0.0009).

Significance: MEG epileptiform discharges of short duration and steep tilt characterize FCD, especially when located at the superficial neocortical gyrus. We speculate that this particular spike morphology results from the intrinsic epileptogenicity of FCD. Morphological analysis of MEG spikes can evaluate the etiology of epileptogenic lesions and detect a strong, localized epileptogenic focus such as that typically observed in FCD.
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August 2015

Advantageous information provided by magnetoencephalography for patients with neocortical epilepsy.

Brain Dev 2015 Feb 10;37(2):237-42. Epub 2014 May 10.

Department of Pediatrics, Hokkaido University Graduate School of Medicine, Sapporo, Japan; Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.

Purpose: We evaluated whether magnetoencephalography (MEG), in addition to surgery, was valuable for the diagnosis and management of epileptic syndromes in patients with neocortical epilepsy (NE).

Methods: We studied MEG in 73 patients (29 females; aged 1-26years; mean 10.3years) for the clinical diagnosis of epilepsy and for preoperative evaluation. MEG data were recorded by 204-channel whole head gradiometers with a 600Hz sampling rate. MEG spike sources were localized on magnetic resonance images (MRI) using a single dipole model to project equivalent current dipoles.

Results: MEG localized an epileptic focus with single clustered dipoles in 24 (33%) of 73 NE patients: 16 (25%) of 64 symptomatic localization-related epilepsy (SLRE) patients and eight (89%) of nine idiopathic localization-related epilepsy (ILRE) patients. MEG provided advantageous information in 12 (50%) of 24 patients with clustered dipoles and confirmed the diagnosis in the remaining 12 (50%). Furthermore, the use of MEG resulted in changes to surgical treatments in nine (38%) patients and in medical management in eight (33%). MEG confirmed the diagnosis in eight (16%) of 49 patients with scattered dipoles. MRI identified a single lesion (28 patients, 38%), multiple lesions (5, 7%), and no lesion (40, 55%). MRI provided confirming information in 19 of 28 patients with a single lesion and 18 of them required surgical resections. MRI did not provide any supportive information in 54 (74%) patients with a single (9), multiple (5) and no lesion (40).

Conclusion: Our study shows that MEG provides fundamental information to aid the choice of diagnostic and therapeutic procedures including changes in medication in addition to surgical treatments for NE.
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February 2015

Magnetoencephalographic analysis of paroxysmal fast activity in patients with epileptic spasms.

Epilepsy Res 2013 Mar 5;104(1-2):68-77. Epub 2012 Oct 5.

Department of Pediatrics, Hokkaido University Graduate School of Medicine, Japan.

Purpose: This study sought to demonstrate the origin and propagation of paroxysmal fast activity (PFA) in patients with epileptic spasms (ESs), using time-frequency analyses of magnetoencephalogram (MEG) PFA recordings.

Methods: A 204-channel helmet-shaped MEG, with a 600Hz sampling rate, was used to examine PFA in 3 children with ESs. We analyzed MEG recordings of PFA by short-time Fourier transform and the aberrant area or high-power spectrum was superimposed onto reconstructed three-dimensional magnetic resonance images as moving images. One ictal discharge was collected. One child and one adult with PFA due to Lennox-Gastaut syndrome were also examined for comparison.

Results: All four PFAs in Patient 1 and five PFAs in Patient 3 were generated from one hemisphere. In Patient 2, four of seven PFAs were generated from one hemisphere and the remaining three were generated from both hemispheres. In Patient 3, one ictal MEG showed ictal discharges that were generated from the same area as the PFA, although the electroencephalogram showed no discharge. In Patients with Lennox-Gastaut syndrome, all 10 PFAs were generated from bilateral hemispheres simultaneously.

Conclusion: Short-time Fourier transform analyses of MEG PFA can show the origin and form of propagation of PFA. These results suggest that ESs are representative of focal seizures and the mechanism of PFA is different between ESs and Lennox-Gastaut syndrome.
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March 2013

The applications of time-frequency analyses to ictal magnetoencephalography in neocortical epilepsy.

Epilepsy Res 2010 Aug 1;90(3):199-206. Epub 2010 Jun 1.

Department of Pediatrics, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.

Purpose: Ictal magenetoencephalographic (MEG) discharges convey significant information about ictal onset and propagation, but there is no established method for analyzing ictal MEG. This study sought to clarify the usefulness of time-frequency analyses using short-time Fourier transform (STFT) for ictal onset and propagation of ictal MEG activity in patients with neocortical epilepsy.

Methods: Four ictal MEG discharges in two patients with perirolandic epilepsy and one with frontal lobe epilepsy (FLE) were evaluated by time-frequency analyses using STFT. Prominent oscillation bands were collected manually and the magnitudes of those specific bands were superimposed on individual 3D-magnetic resonance images.

Results: STFT showed specific rhythmic activities from alpha to beta bands at the magnetological onset in all four ictal MEG records. Those activities were located at the vicinity of interictal spike sources, as estimated by the single dipole method (SDM), and two of the four ictal rhythmic activities promptly propagated to ipsilateral or bilateral cerebral cortices. The patients with FLE and perirolandic epilepsy underwent frontal lobectomy and resection of primary motor area, respectively including the origin of high-magnitude areas of a specific band indicated by STFT, and have been seizure free after the surgery.

Conclusions: STFT for ictal MEG discharges readily demonstrated the ictal onset and propagation. These data were important for decisions on surgical procedure and extent of resection. Ictal MEG analyses using STFT could provide a powerful tool for noninvasive evaluation of ictal onset zone.
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August 2010

Generalized spike-wave discharges involve a default mode network in patients with juvenile absence epilepsy: a MEG study.

Epilepsy Res 2010 May 12;89(2-3):176-84. Epub 2010 Jan 12.

Department of Psychiatry and Neurology, Hokkaido University School of Medicine, North 15, West 7, Sapporo 060-8638, Japan.

This study uses magnetoencephalography (MEG) to examine whether cortical regions that constitute a default mode network are involved during generalized spike-wave discharges (GSWs) in patients with juvenile absence epilepsy (JAE). We studied five JAE patients for whom MEG was recorded using a 204-channel, whole-head gradiometer system. Dynamic statistical parametric mapping (dSPM) was done to estimate the cortical source distribution of GSW. The dSPM results showed strong medial prefrontal activation in all patients, with activation in the posterior cingulate and precuneus in three of five patients simultaneously or slightly after medial prefrontal activation. Furthermore, dSPM showed that the initial activation of a GSW appears in the focal cortical regions. Cortical regions that constitute a default mode network are strongly involved in the GSW process in some patients with JAE. Results also show that focal cortical activation appears at the onset of a GSW.
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May 2010

MEG time-frequency analyses for pre- and post-surgical evaluation of patients with epileptic rhythmic fast activity.

Epilepsy Res 2010 Feb 6;88(2-3):100-7. Epub 2009 Nov 6.

Department of Pediatrics, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan.

Purpose: To evaluate the effectiveness of surgery for epilepsy, we analyzed rhythmic fast activity by magnetoencephalography (MEG) before and after surgery using time-frequency analysis. To assess reliability, the results obtained by pre-surgical MEG and intraoperative electrocorticography were compared.

Methods: Four children with symptomatic localization-related epilepsy caused by circumscribed cortical lesion were examined in the present study using 204-channel helmet-shaped MEG with a sampling rate of 600Hz. One patient had dysembryoplastic neuroepithelial tumor (DNT) and three patients had focal cortical dysplasia (FCD). Aberrant areas were superimposed, to reconstruct 3D MRI images, and illustrated as moving images.

Results: In three patients, short-time Fourier transform (STFT) analyses of MEG showed rhythmic activities just above the lesion with FCD and in the vicinity of DNT. In one patient with FCD in the medial temporal lobe, rhythmic activity appeared in the ipsilateral frontal lobe and temporal lateral aspect. These findings correlate well with the results obtained by intraoperative electrocorticography. After the surgery, three patients were relieved of their seizures, and the area of rhythmic MEG activity disappeared or become smaller. One patient had residual rhythmic MEG activity, and she suffered from seizure relapse.

Conclusion: Time-frequency analyses using STFT successfully depicted MEG rhythmic fast activity, and would provide valuable information for pre- and post-surgical evaluations to define surgical strategies for patients with epilepsy.
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February 2010

Aberrant somatosensory-evoked responses imply GABAergic dysfunction in Angelman syndrome.

Neuroimage 2008 Jan 15;39(2):593-9. Epub 2007 Sep 15.

Department of Pediatrics, Hokkaido University Graduate School of Medicine, North 15, West 7, Kita-ku, Sapporo, 060-8638, Japan.

A role for gamma-aminobutyric acid (GABA)ergic inhibition in cortical sensory processing is one of the principle concerns of brain research. Angelman syndrome (AS) is thought to be one of the few neurodevelopmental disorders with GABAergic-related genetic involvement. AS results from a functional deficit of the imprinted UBE3A gene, located at 15q11-q13, resulting mainly from a 4-Mb deletion that includes GABA(A) receptor subunit genes. These genes are believed to affect the GABAergic system and modulate the clinical severity of AS. To understand the underlying cortical dysfunction, we have investigated the primary somatosensory-evoked responses in AS patients. Subjects included eleven AS patients with a 15q11-q13 deletion (AS Del), two AS patients without a 15q11-q13 deletion, but with a UBE3A mutation (AS non-Del), six epilepsy patients (non-AS) and eleven normal control subjects. Somatosensory-evoked fields (SEFs) in response to median nerve stimulation were measured by magnetoencephalography. The N1m peak latency in AS Del patients was significantly longer (34.6+/-4.8 ms) than in non-AS patients (19.5+/-1.2 ms, P<0.001) or normal control subjects (18.4+/-1.8 ms, P<0.001). The next component, P1m, was prolonged and ambiguous and was only detected in patients taking clonazepam. In contrast, SEF waveforms of AS non-Del patients were similar to those of control individuals, rather than to AS Del patients. Thus, GABAergic dysfunction in AS Del patients is likely due to hemizygosity of GABA(A) receptor subunit genes, suggesting that GABAergic inhibition plays an important role in synchronous activity of human sensory systems.
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January 2008